The SMA (Subminiature A) connector was originally designed by Bendix Scintilla Corporation, and is one of the most commonly used RF/microwave connectors. A standard SMA connector is designed for interconnects to 12.4 GHz. Fortunately, a good SMA is useable to 18 GHz in most cables, and if well constructed with greater loss and lower return loss to 24 GHz.
Among the SMA connectors, board mount type SMA connectors mounted on a board such as PCB are typically classified into a vertical mount straight PCB jack and a right angle PCB jack. FIG. 1 shows a conventional straight SMA coaxial connector, whereas FIG. 2 shows a conventional right angle SMA coaxial connector.
Referring to FIGS. 1a to 1d, a conventional straight coaxial connector 10 includes a cylindrical body 12, a main body 14, a central conductor 16, and ground legs 18. The cylindrical body 12 has spiral threads 13 thereon, and contains a terminal 11 surrounded with a dielectric 15 therein. The terminal 11 is connected to the central conductor 16. The central conductor 16 and the ground legs 18 are protruded from the main body 14 in the counter direction of the cylindrical body 12. The ground legs 18 are composed of four legs 18a˜18d disposed at four corners of the main body 14.
As shown in FIGS. 1d to 1f, this conventional coaxial connector 10 is vertically surface-mounted to a board 30, such as PCB, on which circuit patterns 32 are formed. The central conductor 16 and the ground legs 18 are inserted into through holes 36 and 38a˜38d, respectively, and then joined to the board 30 by solder 35 and 37 on the rear side of the board 30.
A conventional right angle coaxial connector 20 shown in FIGS. 2a to 2c is vertically surface-mounted to the board, in the same way as the connector 10 shown in FIG. 1. However, contrary to the connector 10 in FIG. 1, a cylindrical body 22 is configured at a right angle to a main body 24. A central conductor 26 and ground legs 28 are similar in structure to those of the connector in FIG. 1. Since the above-discussed conventional connectors, shown in FIGS. 1 and 2, can be mounted to a surface as well as edges of the board, there is sufficient board space to receive the connectors. However, the straight SMA connector 10 shown in FIG. 1 may have poor electrical characteristics by increased inductance in high frequency region because the central conductor 16 is connected via the through holes 36 and 38 of the board 30. So, this type connector may be not suitable for high frequency, for example, 3 GHz or more. And also, the right angle SMA connector 20 shown in FIG. 2 may be not suitable for high frequency because the central conductor 26 is extended at a right angle to the terminal.